The present invention relates to a method for transcripting a fine pattern formed on a stamper to the surface of a target of transcription and an apparatus therefor.
In recent years, semiconductor integrated circuits have been increasingly microminiaturized and their designs have been made more and more dense. As a pattern transcription technology for implementing fine patterning therefor, accuracy of photolithography equipment has been increased. The processing methods have been brought close to the wavelength of light sources for light exposure and lithography technologies are approaching their limits. To cope with this, electron beam lithography systems, which are a type of charged particle beam system, have taken over lithography technologies to accelerate further microminiaturization and accuracy enhancement.
In pattern formation using electron beams, a mask pattern is lithographed unlike one-shot exposure methods in pattern formation using such a light source as i-ray and excimer laser. Therefore, exposure (lithography) takes more time as the number of patterns to be lithographed is increased and it is believed that necessity for much time in pattern formation is a disadvantage of electron beam lithography. For this reason, as the scale of integration is dramatically increased to 256 mega to 1 giga to 4 giga, the pattern formation time is accordingly dramatically lengthened. There is apprehension that throughputs are significantly degraded. Consequently, to accelerate electron beam lithography systems, cell projection lithography is being developed. In the cell projection lithography, masks in various shapes are combined and electron beams are applied to them in a lump to form an electron beam in a complicated shape. As a result, while the microminiaturization of patterns has been facilitated, a disadvantage of increased equipment cost has been brought about. For example, it is inevitable to increase the size of each electron beam lithography system and a mechanism for accurately controlling mask positions is required.
Meanwhile, there are imprint technologies for forming fine patterns at low cast. In these technologies, a stamper having recesses and projections patterned similarly to a pattern desired to be formed over a substrate is pressed against a resist film layer formed over the surface of the substrate as the target of transcription. Thereafter, the stamper is broken away and a desired pattern is thereby transcripted onto the resist. A silicon wafer is used as the stamper and a fine pattern not more than 25 nanometers can be formed by transcription. With respect to the imprint technology, consideration has been given to application thereof to the formation of recording bits in large-capacity recording media, the formation of semiconductor integrated circuit patterns, and the like.
To accurately transcript a fine pattern onto a large-capacity recording medium substrate or a semiconductor integrated circuit substrate by the imprint technology, it is necessary to take the following measure: a stamper is pressed so that pressure is evenly applied to a pattern transcription area over the surface of a substrate as the target of transcription which is slightly undulated.
Japanese Unexamined Patent Publication No. 2004-303385 describes an invention relating to the prevention of the ingress of air bubbles due to superficial slight undulation by taking the following measure in a manufacturing method for optical disks: transcription is carried out while a warp is produced in the master.
US Patent Publication No. 2008/0229948A1 and Japanese Unexamined Patent Publication No. 2006-018975 describe inventions in which the ingress of air bubbles due to superficial slight undulation is prevented by taking the following measure: transcription is carried out while pressure is applied by a fluid to bend a stamper.
Japanese Unexamined Patent Publication No. 2009-220559 describes an invention relating to a technology for transcripting fine patterns by nanoimprinting. In this technology, the ingress of air bubbles due to superficial slight undulation is prevented to uniformly transcript a pattern by carrying out the transcription in vacuum or liquefied gas.
However, the transcription method described in Japanese Unexamined Patent Publication No. 2004-303385 uses mechanical fixture and does not take into account the influence of dusting at a slide part between the fixture and a stamper. It does not take the following into account, either: it is difficult to continuously deform the master by a small amount and this causes unevenness in the wetting and spreading of resist.
According to the transcription methods described in the US Patent Publication No. 2008/0229948A1 and Japanese Unexamined Patent Publication No. 2006-018975, the formation of air bubbles due to superficial slight undulation can be suppressed by using a fluid to make a stamper surface spherical. However, these methods involve the problems of degradation in the cleanliness of an environment by dusting due to leakage of a fluid, the complication of a structure, and the like.
According to the method described in Japanese Unexamined Patent Publication No. 2009-220559, the ingress of air bubbles due to superficial slight undulation can be prevented by bringing the atmosphere under vacuum. However, this method involves the following problems: the entire system must be placed in a vacuum chamber and this increases the size of equipment and loading to and unloading from the vacuum chamber take time and this degrades the overall throughput.